Experience-dependent plasticity modulates ongoing activity in the antennal lobe and enhances odor representations

Ongoing neural activity has been observed across several brain regions and
is thought to reflect the internal state of the brain. Yet, it is
important to understand how ongoing neural activity interacts with sensory
experience, and shapes sensory representations. Here, we show that
projection neurons of the fruit fly antennal lobe exhibit spatiotemporally
organized ongoing activity. After repeated exposure to odors, we observe a
gradual and cumulative decrease in the amplitude and number of calcium
events occurring in the absence of odor stimulation, as well as a
reorganization of correlations between olfactory glomeruli. Accompanying
these plastic changes, we find that repeated odor experience reduces
trial-to-trial variability and enhances the specificity of odor
representations. Our results reveal an odor experience-dependent
modulation of ongoing and sensory-evoked activity at peripheral levels of
the fruit fly olfactory system.